Here at 21.co.uk, our Slingo casino games are some of the most popular on-site! On this occasion, Slingo has taken the form of one of the most popular slot games in the world. Reel King is a retro-themed slot that is established due to one brilliant new feature and that is the 'Reel King' feature. In this Slingo classic, it acts as a secondary goal for big wins. Land enough wins on the Slingo card to progress up to a full house for the maximum win. Reel King was already a very reputable online casino game, but this Slingo rendition may be our favourite.